Overview
IEC TS 62607-6-8:2023 specifies an in-line four-point probe (4PP) method to determine the key control characteristic sheet resistance (RS) of graphene. The specification defines how to derive RS (in ohm per square, Ω/sq) from four‑terminal resistance measurements using four electrodes placed on the planar sample surface. The method covers a wide measurement range (10−2 Ω/sq to 10^4 Ω/sq) and is applicable to CVD graphene transferred to insulating substrates (quartz, SiO2 on Si) and graphene grown from silicon carbide.
Keywords: IEC TS 62607-6-8, graphene sheet resistance, in-line four-point probe, 4PP, RS, CVD graphene, quartz, SiO2 on Si, van der Pauw.
Key topics and technical requirements
- Measurement principle: Four‑terminal electrical resistance measurements using four surface probes to minimize contact resistance and derive sheet resistance.
- Scope of applicability: Planar graphene samples with isotropic conductivity; CVD graphene on quartz or other insulating supports; graphene on SiC.
- Measurement range: 10−2 Ω/sq to 10^4 Ω/sq.
- Sampling and spatial resolution: Method supports mapping via a sampling plan; spatial resolution depends on probe geometry and sampling density.
- Calibration and accuracy: Procedures for instrument calibration, uncertainty estimation, and measurement accuracy are specified.
- Ambient influences: Annex A discusses effects of temperature and relative humidity on graphene resistance measurements.
- Special cases: Annex B covers non‑equidistant probes, proximity to sample edge, and combined non‑ideal probe geometries.
- Reporting requirements: Section 7 defines required reporting (cover sheet, product/sample identification, measurement conditions, measurement results).
Practical applications and users
- Quality control in production: Manufacturers of graphene films and devices (roll‑to‑roll CVD producers) use the 4PP method for inline process control of electrical uniformity.
- Research and development: R&D labs characterizing CVD graphene and graphene-on‑SiC for device prototyping and materials optimization.
- Metrology and test labs: Calibration and conformity testing where non‑contact or boundary contacts (van der Pauw) are impractical.
- Device integration teams: Engineers validating conductive properties of graphene on insulating substrates for sensors, transparent conductors, and flexible electronics.
Benefits include a fast, easy‑to‑implement method with minimized contact resistance and the ability to map sheet resistance over arbitrary sample shapes.
Related standards
- IEC 62607-6-7 (van der Pauw method) - complementary method for sheet resistance measurement when placing contacts on sample boundaries is feasible.
- Annex D of IEC TS 62607-6-8 lists other standards related to sheet resistance measurement and metrology.
For implementers, this Technical Specification provides standardized measurement protocol, calibration guidance, and reporting templates to ensure reproducible, comparable graphene sheet resistance data across labs and production lines.